From 057722bbf43ed51f518839b5ffbb52716aa81420 Mon Sep 17 00:00:00 2001
From: Chris Lu <chris.lu@gmail.com>
Date: Sun, 29 Mar 2020 00:54:39 -0700
Subject: [PATCH] return part of the chunk if chunkview is not the full chunk

---
 weed/filesys/reader_at.go | 36 ++++++++++++++++++++++++------------
 weed/util/http_util.go    | 12 ++++++++----
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/weed/filesys/reader_at.go b/weed/filesys/reader_at.go
index c95b6cdb9..f819a3fa6 100644
--- a/weed/filesys/reader_at.go
+++ b/weed/filesys/reader_at.go
@@ -102,34 +102,46 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 
 }
 
-func (c *ChunkReadAt) fetchChunkData(chunkView *filer2.ChunkView) ([]byte, error) {
+func (c *ChunkReadAt) fetchChunkData(chunkView *filer2.ChunkView) (data []byte, err error) {
 
 	// fmt.Printf("fetching %s [%d,%d)\n", chunkView.FileId, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size))
 
 	chunkData := c.chunkCache.GetChunk(chunkView.FileId)
 	if chunkData != nil {
 		glog.V(3).Infof("cache hit %s [%d,%d)", chunkView.FileId, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size))
-		return chunkData, nil
+	} else {
+		chunkData, err = c.doFetchFullChunkData(chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped)
+		if err != nil {
+			return nil, err
+		}
 	}
 
-	urlString, err := c.lookupFileId(chunkView.FileId)
+	if int64(len(chunkData)) < chunkView.Offset+int64(chunkView.Size) {
+		return nil, fmt.Errorf("unexpected larger chunkView [%d,%d) than chunk %d", chunkView.Offset, chunkView.Offset+int64(chunkView.Size), len(chunkData))
+	}
+
+	data = chunkData[chunkView.Offset : chunkView.Offset+int64(chunkView.Size)]
+
+	c.chunkCache.SetChunk(chunkView.FileId, chunkData)
+
+	return data, nil
+}
+
+func (c *ChunkReadAt) doFetchFullChunkData(fileId string, cipherKey []byte, isGzipped bool) ([]byte, error) {
+
+	urlString, err := c.lookupFileId(fileId)
 	if err != nil {
-		glog.V(1).Infof("operation LookupFileId %s failed, err: %v", chunkView.FileId, err)
+		glog.V(1).Infof("operation LookupFileId %s failed, err: %v", fileId, err)
 		return nil, err
 	}
 	var buffer bytes.Buffer
-	err = util.ReadUrlAsStream(urlString, chunkView.CipherKey, chunkView.IsGzipped, chunkView.IsFullChunk, chunkView.Offset, int(chunkView.Size), func(data []byte) {
+	err = util.ReadUrlAsStream(urlString, cipherKey, isGzipped, true, 0, 0, func(data []byte) {
 		buffer.Write(data)
 	})
 	if err != nil {
-		glog.V(1).Infof("read %s failed, err: %v", chunkView.FileId, err)
+		glog.V(1).Infof("read %s failed, err: %v", fileId, err)
 		return nil, err
 	}
 
-	glog.V(3).Infof("read %s [%d,%d)", chunkView.FileId, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size))
-
-	chunkData = buffer.Bytes()
-	c.chunkCache.SetChunk(chunkView.FileId, chunkData)
-
-	return chunkData, nil
+	return buffer.Bytes(), nil
 }
diff --git a/weed/util/http_util.go b/weed/util/http_util.go
index 750516b92..4b1a7b895 100644
--- a/weed/util/http_util.go
+++ b/weed/util/http_util.go
@@ -193,7 +193,7 @@ func ReadUrl(fileUrl string, cipherKey []byte, isGzipped bool, isFullChunk bool,
 
 	if cipherKey != nil {
 		var n int
-		err := readEncryptedUrl(fileUrl, cipherKey, isGzipped, offset, size, func(data []byte) {
+		err := readEncryptedUrl(fileUrl, cipherKey, isGzipped, isFullChunk, offset, size, func(data []byte) {
 			n = copy(buf, data)
 		})
 		return int64(n), err
@@ -261,7 +261,7 @@ func ReadUrl(fileUrl string, cipherKey []byte, isGzipped bool, isFullChunk bool,
 func ReadUrlAsStream(fileUrl string, cipherKey []byte, isContentGzipped bool, isFullChunk bool, offset int64, size int, fn func(data []byte)) error {
 
 	if cipherKey != nil {
-		return readEncryptedUrl(fileUrl, cipherKey, isContentGzipped, offset, size, fn)
+		return readEncryptedUrl(fileUrl, cipherKey, isContentGzipped, isFullChunk, offset, size, fn)
 	}
 
 	req, err := http.NewRequest("GET", fileUrl, nil)
@@ -300,7 +300,7 @@ func ReadUrlAsStream(fileUrl string, cipherKey []byte, isContentGzipped bool, is
 
 }
 
-func readEncryptedUrl(fileUrl string, cipherKey []byte, isContentGzipped bool, offset int64, size int, fn func(data []byte)) error {
+func readEncryptedUrl(fileUrl string, cipherKey []byte, isContentGzipped bool, isFullChunk bool, offset int64, size int, fn func(data []byte)) error {
 	encryptedData, err := Get(fileUrl)
 	if err != nil {
 		return fmt.Errorf("fetch %s: %v", fileUrl, err)
@@ -318,7 +318,11 @@ func readEncryptedUrl(fileUrl string, cipherKey []byte, isContentGzipped bool, o
 	if len(decryptedData) < int(offset)+size {
 		return fmt.Errorf("read decrypted %s size %d [%d, %d)", fileUrl, len(decryptedData), offset, int(offset)+size)
 	}
-	fn(decryptedData[int(offset) : int(offset)+size])
+	if isFullChunk {
+		fn(decryptedData)
+	} else {
+		fn(decryptedData[int(offset) : int(offset)+size])
+	}
 	return nil
 }